Silent Spring’s principal popular effect was to brand DDT as dangerous to bird populations. The mechanism by which DDT does this is now largely, but not completely, understood. In summary, it interferes with the delivery of calcium carbonate to the eggshell gland, and the eggs that are laid have thinner shells. Shells that are too thin can lead to the death of the embryo. This eggshell thinning is the primary environmental concern over DDT.
It’s been about five decades since Silent Spring was published, and we’ve learned a lot in those years. One thing we’ve learned is that DDT is only one of many causes of eggshell thinning. Other culprits include lead and mercury toxicity, oil, phosphorus and calcium deficiency, and dehydration. Perhaps most significantly, birds in captivity in order to undergo testing are under stress, and this stress alone is enough to produce eggshell thinning. Although DDT’s mechanism for eggshell thinning is plausible, many studies throughout the 1970’s and 1980’s failed to correlate such thinning with high levels of DDT, even extremely high levels. Other studies have confirmed Rachel Carson’s findings. My own conclusion based on a review is that there probably is a correlation, but it’s not a strong one; and at best it’s only one of many causes. Whether DDT is used or not would probably not have a large impact on bird populations.
But despite the likelihood that it would have some impact, it’s now known that the species Rachel Carson focused on (most notably bald eagles) were already in massive decline from unrelated pressures even before DDT’s introduction. Habitat loss and hunting had been, by far, the greater causes of bald eagle deaths. Hunting had reduced the populations to just a few hundred nesting pairs in the mountains, and lowland eagles were already gone from habitat loss. Rachel Carson did not ignore these issues in her book, but the popular perception that banning DDT was all that was needed to magically restore bald eagle populations was naïve. In the end, it was the Bald Eagle Protection Act and the bird’s 1967 placement on the endangered species list, combined with increased penalties for poaching, that ultimately led to the bald eagle’s successful return to remaining habitats.
Brown pelicans are another species often cited as having been decimated by DDT use in the United States, along the Gulf coast and in California. Massive declines were indeed correlated with DDT use, but it may have been a coincidence in each case. Along the Gulf coast, hunting by angry fishermen had reduced the pelican population in Texas from 5,000 annual births to just 200 in 1941. DDT certainly didn’t help; but it was another case where the bird populations would have dropped sharply whether DDT was in the picture or not.
Of course, it would be completely wrong to overlook DDT’s potential for causing harm simply because there are other things that cause harm too. All we can do is our best to quantify exactly what the risk really is, and then the decision to ban or not to ban becomes a cost/benefit analysis, which is no longer a science question. Everyone has the right to their own opinion on what’s most important, and in the United States, we chose the birds.
Silent Spring’s legacy may have been good for the birds, but not so much for human populations in the third world. DDT is one of the most effective pesticides ever discovered for fighting malaria. Although DDT remains legal for insecticide use in most areas where malaria is a major killer, the money for fighting the mosquitos often comes from donors in wealthy countries like the United States. Such wealthy donors have often had little personal exposure to the issues, and can sometimes have a skewed perspective when it comes to bald eagle eggshells in the United States versus the deaths of children in Mozambique. Writing in the Nature Medicine journal, malaria advocate Prof. Amir Attaran criticized American environmental groups for opposing the public health exceptions of DDT bans:
“Environmentalists in rich, developed countries gain nothing from DDT, and thus small risks felt at home loom larger than health benefits for the poor tropics. More than 200 environmental groups, including Greenpeace, Physicians for Social Responsibility and the World Wildlife Fund, actively condemn DDT.”
As a result of these pressures, many donations now coming from wealthy nations are now contingent upon DDT not being used, which leaves the poor nations with fewer options, often too expensive and less effective, and children die. Up to three million people die of malaria each year, most of them in Africa. DDT, while it does have environmental and health concerns like all pesticides, is not known to have ever killed anyone. If we shelve our most effective tools hoping that something perfect will come along that has no potential downside, we’ll wait forever, and thousands will continue dying every day. These are the cases where wealthy environmental groups appear to do their best to justify their elitist stereotype, at the expense of brown people. (The World Health Organization’s ban on DDT does include limited exemptions for malaria control in many regions, but money for its use still often depends on qualified foreign aid. In Africa, the exemption allows indoor use only, like wearing armor on half your body.)
Rachel Carson absolutely acknowledged DDT’s importance to fighting malaria, but was quick to point out another downside: acquired resistance. After six or seven years, mosquito populations develop resistance to DDT. However, this is the case with all pesticides, it is not a reason to avoid DDT per se. Moreover, we’ve since learned that it is still effective against resistant mosquitos, only a little less so. Susceptibility in resistant strains goes down to 63%, as opposed to 87% in non-resistant strains.
Even among resistant mosquitos, DDT is an exceptionally effective repellent. Houses treated with DDT are avoided by all mosquitos, resistant or not.
But like all synthetic chemicals, DDT has been blamed for virtually any human illness imaginable. Some say it causes cancer, diabetes, hyperthyroidism, loss of fertility, that it functions as an endocrine disruptor, and more. The World Health Organization classifies it only as “moderately hazardous”, and in response to all the wildly conflicting studies of its cancer-causing effects in animal tests, the U.S. Environmental Protection Agency classifies it as a “probable carcinogen”. The claims that DDT definitely causes cancer or anything else are not supported by the data, but obviously it’s a risky compound that we don’t want to expose anyone to if we don’t have to. And so, again, we’re outside of science questions, and down to risk assessment.
DDT does have its place, and its current usage is probably not too far off of what it should be. The exception is Africa where DDT’s upside far outweighs the down, and my opinion is that donors should relax their restrictions against it, and leave those decisions to the experts on the front lines in Africa. For much of the rest of the world, DDT has largely been supplanted by newer and better agricultural pesticides, and there’s insufficient reason to put collateral species under pressure. A scientific review nearly always produces better focused policy, and our DDT policy is definitely due for a tune-up.
REFERENCES & FURTHER READING
Attaran, A., Roberts, D., Curtis, C., Kilama, W. “Balancing risks on the backs of the poor.” Nature Medicine. 1 Jan. 2000, Number 6: 729-731.
Campbell, L. Endangered and threatened animals of Texas: Their life history and management. Austin: Texas Parks & Wildlife, Resource Protection Division, Endangered Resources Branch, 1995. 58.
Carson, R. Silent Spring. New York: Fawcett Crest, 1964.
Edwards, J., Milloy, S. “100 things you should know about DDT.” JunkScience.com. Steven J. Milloy, 7 Jan. 2007. Web. 2 Nov. 2010.
EPA. “DDT - A Brief History and Status.” Pesticides: Topical & Chemical Fact Sheets. US Environmental Protection Agency, 16 Jan. 2008. Web. 9 Dec. 2010.
Gates Foundation. “Our Work in Neglected Diseases: Visceral Leishmaniasis, Guinea Worm, Rabies - Overview & Approach.” Bill & Melinda Gates Foundation. Bill & Melinda Gates Foundation, 14 Jun. 2010. Web. 30 Oct. 2010.
Gladwell, M. “The Mosquito Kil
ler.” The New Yorker. 2 Jul. 2001, Annals of Public Health: 42.
Miller, H. “Utterly Repellent.” Forbes.com. Forbes.com LLC, 24 Feb. 2010. Web. 29 Oct. 2010.
Stokstad, E. “Can the Bald Eagle Still Soar After It Is Delisted?” Science. 22 Jun. 2007, Volume 316, Number 5832: 1689-1690.
42. THE MYSTERY OF STENDEC
What was the significance of this mysterious final transmission of an airliner just before its crash?
It was a story borne out all too often in the annals of aviation disasters. An aircraft finds itself off-course and in the clouds with zero visibility, and worse, surrounded by mountain peaks that can’t be seen. That’s what happened on August 2, 1947, in the Andes Mountains of western Argentina. An Avro Lancastrian passenger plane of British South American Airways with 11 people on board struck a mountainside in zero visibility while descending toward what it thought was Chile. All aboard were presumed killed, with the crash not even being confirmed until more than fifty years later when its wreckage was finally found.
By themselves, the basic facts of what happened to British South American Flight CS-59 are tragic but not especially mysterious. The cause of the crash was a controlled flight into terrain. Nothing was broken, nothing was wrong, and it’s unlikely the crew even saw the crash coming until the near-vertical cliff near the summit of Tupungato Mountain appeared through the mist. A second later, the Lancastrian was in a billion torn pieces, sliding down the face in an avalanche of its own making. Those pieces began to emerge from the bottom of the glacier, bit by bit, around the year 2000.
The mysterious part is what came over the radio just before the crash. In those days, long distance communication was by Morse code. The crew had been making regular hourly reports of its speed, position, and altitude, and all was well. At 5:41pm, four minutes before their anticipated landing time, the radio operator, Dennis Harmer, sent their ETA as 5:45pm and concluded it with the phrase STENDEC:
... - . -. -.. . -.-.
The Chilean Air Force ground controller asked him to repeat that, and Harmer sent it twice more, STENDEC, STENDEC.
And that was the last anyone ever heard of Flight CS-59. The mystery of the word STENDEC took its place among the great unsolved cases so beloved in the lore of urban legendry.
Avro Lancastrian
The Avro Lancastrian began its life as a British Lancaster bomber in World War II. Lancasters had four Rolls Royce Merlin engines, the front-line combat engine that powered the latest Spitfire and Mustang fighters. With some 5,000 horsepower on tap, Lancastrians were in demand for civilian applications after the war, such as the route over the Andes. The crew and passengers of Flight CS-59 had in fact just crossed the Atlantic from London on board an Avro York, a slightly different variant of the Lancaster; then changed planes to the Lancastrian for the final leg.
The JIAAC (the Argentinian Civil Aviation Accident Investigation Board) found the probable cause of the crash, but only after examining the wreckage upon its 2000 discovery. In CS-59’s day, navigation was done by dead reckoning, making time/speed/distance calculations, as there were no radio beacons to help determine position. Flying east to west across South America, a plane must fight the jet stream head on. If the jet stream is faster than expected, dead reckoning calculations will lead you to believe that you’ve gone further than you actually have. Flight CS-59 had been in the air long enough to clear the Andes, and with no visual cues, began its descent into Chile, down into the clouds. Unfortunately, they descended right into a collision course with Tupungato. Once they entered its wind shadow, they fell victim to a phenomenon called a lee wave, part of which involves a downdraft over the face of the mountain, and at that point a crash became unavoidable. Without visibility, they almost certainly never saw it coming, and couldn’t have done anything about it even if they had. These are precisely the same conditions that caused the 1972 crash of the Uruguayan Rugby team that inspired the book and movie Alive.
CS-59’s crew were all experienced Royal Air Force pilots who had flown against the Germans in World War II. The pilot, Reginald Cook, had flown more than 90 combat missions. Cook’s first officer Norman Hilton-Cook and second officer Donald Checklin each had over 2,000 flight hours. Dennis Harmer had served as a radio operator for three years during the war, and for over 600 hours for the airline. Among the crew, they had some 30 crossings of the Andes Mountains, though this was Cook’s first time as captain.
Certainly such a crew would have been aware of the jet stream and lee waves, but none had ever negotiated the Andes before without an experienced captain. Although the cause of the crash was navigational error coupled with pilot error, the crew did about as well as anyone could have done, given the technology of the time, and the weather conditions nature thrust them into.
But the 2000 finding of the true cause of the crash has not stemmed the speculation about what significance STENDEC had. Theories even extended to UFOs, with some people proposing the cryptic message must have been some kind of warning about the plane’s abduction by a giant alien craft. Even aviation medical experts have gotten into the fray, suggesting that the crew may have been suffering from hypoxia. Lancastrians were not pressurized but the crew did wear oxygen masks, and perhaps Harmer was not wearing his or it had malfunctioned. But if this was the reason for his garbled transmission, it seems unlikely that he could have repeated it verbatim, twice, when asked by the Chilean controller.
All kinds of people have made all kinds of guesses about what STENDEC might have meant. None of them are very convincing. Most interesting is that the letters are an anagram of DESCENT, and Flight CS-59 was certainly on its descent. Did Harmer simply miskey the letters of DESCENT? It seems to be quite a stretch that such an experienced operator would have made the exact same extreme misspelling three times in a row. Moreover, it would have been a totally random place in the transmission to throw in this word. Nobody ever did that.
It’s also been proposed that Harmer miskeyed the Aircraft’s name, which was Star Dust (all of British South American Airways’ aircraft were given two-word names beginning with Star). This possible misspelling has been a popular theory, so much so that most stories you’ll find about Flight CS-59 are titled The Mystery of the Star Dust or some such thing. However, in reality, nobody at the time ever referred to the aircraft or the flight by the unofficial name painted on it by the airline. Probably the crew was scarcely even aware of the plane’s name. In radio transmissions of the day, planes were only ever addressed by registration number, in this case G-AGWH. And, once again, it would have been completely random and uncalled for to tack the plane’s name onto the end of a routine transmission.
Most other theories are that STENDEC was an acronym of the first letters of words in some sentence, and various nominations have been proposed. None of them make sense, because no radio operator would ever communicate in such a way, and certainly not repeat it twice more when told that it was not understood.
One fairly bad match is “Santiago tower, now descending entering cloud”, which is true but no sane radio operator should expect such an acronym to be understood. Another is “Star Dust tank empty no diesel expecting crash”, which has five problems: Harmer would not have identified the aircraft by its unofficial name; Star Dust was two words, not one; Merlin engines do not burn diesel; the plane was not low on fuel; and Harmer was experienced enough to know there would be no reasonable expectation of anyone comprehending such an acronym.
Morse code experts have searched for a solution within the subtleties of hand-keyed code. There is an attention-getting signal consisting of three dots followed by a dash:
...-
and these are the same as STENDEC’s first two letters, except that they have a space:
... -
Morse code also uses something called prosigns, which are two letters run together without a space. The prosign AR, which means “End of message”
, looks like this:
.-.-.
and that’s the same as STENDEC’s final two letters, except that, again, they have a short space after the first dot:
. -.-.
So, theoretically, STENDEC could mean ATTENTION – END – END OF MESSAGE. Now, this sounds fairly reasonable. And it could be, except that it wouldn’t make much sense for Harmer to send this. STENDEC followed his transmission of their estimated arrival time, so it would be rather strange for him to insert the ATTENTION signal in the middle of a message. Similarly, it would be redundant to say END and then transmit END OF MESSAGE. None of Harmer’s other transmissions from the flight did this, and no radio operators of the day ever did, so far as I could find. I think we can call this the best effort from the Morse code experts, and it shows that there is probably not a good answer to STENDEC to be found within the imperfections of hand keying.
Is it really necessary to assign some profound significance to STENDEC? What about all the other meaningless, garbled, or unclear radio transmissions that happen every day, that nobody remembers because they’re not followed by a fatal crash? I’ve flown a lot, and I think every time I go up I hear someone say something I can’t make out. I’ve no reason to suspect it was any different in the days of Morse code. Who knows what Harmer meant to say? Most likely, he was about to continue with what would have been a meaningful transmission when it was cut short by the crash. Most of these guys were in their twenties and Harmer could have even just been horsing around. The bottom line is that the cause of the crash had nothing to do with anything Harmer sent or didn’t send on the radio. It would have crashed anyway, and chances are that if Harmer had lived five minutes longer he and the Chilean air traffic controller would have connected a little better, and the miscommunication never would have been remembered.
Skeptoid 4: Astronauts, Aliens, and Ape-Men Page 27